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[24.9.77.57]) by smtp.googlemail.com with ESMTPSA id e1sm28380401iod.17.2020.12.25.12.20.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Dec 2020 12:20:26 -0800 (PST) From: Jim Cromie To: jbaron@akamai.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org Cc: Jim Cromie Subject: [RFC PATCH v2 13/19] dyndbg: verify __dyndbg & __dyndbg_callsite invariant Date: Fri, 25 Dec 2020 13:19:38 -0700 Message-Id: <20201225201944.3701590-14-jim.cromie@gmail.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201225201944.3701590-1-jim.cromie@gmail.com> References: <20201225201944.3701590-1-jim.cromie@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Prove that linker + DECLARE_DYNAMIC_DEBUG_METADATA reliably place the 2 related struct _ddebug* initializations into parallel/ordered slots in the __dyndbg_* sections. This is a step towards dropping the pointer between the 2 structs; maybe the 2 vectors stay ordered, and we can deduce and use N. Of course this test won't survive, since it needs the pointer we seek to drop, but its a start. 0- iterate over __dyndbg_callsite in parallel with __dyndbg rename var: s/iter_start/iter_mod_start/ for clarity, consistency. I disregarded a checkpatch warning about externs in c-files, staying consistent with long-standing code seemed better. 1- prove that iter->site == site_iter. DECLARE_DYNAMIC_DEBUG_METADATA + linker insure this now Maybe we can drop pointer, still get order. WRT the debug-printing, its noisy, but only with verbose=3. It warrants trimming later. The offset grows smoothly, because it is N * sizeof(structs), which differ. It looks reliable. Amend later to do math, converge on truth. If numbers are stable after stripping pointer, we have N. rec ptr mod-ptr N (void*)p [ 1.929072] dyndbg: 2828: ffffffff82b32f28 ffffffff82b32f10 1 24 40 [ 1.929326] dyndbg: 2829: ffffffff82b32f40 ffffffff82b32f10 2 48 80 [ 1.930209] dyndbg: 2 debug prints in module i386 We have N (col 4), and N * structsize (col 5). I feel like it still needs more staring at. Signed-off-by: Jim Cromie --- lib/dynamic_debug.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-) diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c index 2d10fc1e16cd..c1a113460637 100644 --- a/lib/dynamic_debug.c +++ b/lib/dynamic_debug.c @@ -41,6 +41,8 @@ extern struct _ddebug __start___dyndbg[]; extern struct _ddebug __stop___dyndbg[]; +extern struct _ddebug_callsite __start___dyndbg_callsites[]; +extern struct _ddebug_callsite __stop___dyndbg_callsites[]; struct ddebug_table { struct list_head link; @@ -119,6 +121,7 @@ do { \ #define vpr_info(fmt, ...) vnpr_info(1, fmt, ##__VA_ARGS__) #define v2pr_info(fmt, ...) vnpr_info(2, fmt, ##__VA_ARGS__) +#define v3pr_info(fmt, ...) vnpr_info(2, fmt, ##__VA_ARGS__) static void vpr_info_dq(const struct ddebug_query *query, const char *msg) { @@ -1147,7 +1150,8 @@ static int __init dynamic_debug_init_control(void) static int __init dynamic_debug_init(void) { - struct _ddebug *iter, *iter_start; + struct _ddebug *iter, *iter_mod_start; + struct _ddebug_callsite *site, *site_mod_start; const char *modname = NULL; char *cmdline; int ret = 0; @@ -1162,23 +1166,33 @@ static int __init dynamic_debug_init(void) ddebug_init_success = 1; return 0; } - iter = __start___dyndbg; + + iter = iter_mod_start = __start___dyndbg; + site = site_mod_start = __start___dyndbg_callsites; modname = iter->site->modname; - iter_start = iter; - for (; iter < __stop___dyndbg; iter++) { + + for (; iter < __stop___dyndbg; iter++, site++) { + + BUG_ON(site != iter->site); + v3pr_info("%u: %px %ld %ld %ld\n", entries, site, + site - site_mod_start, + ((void *)site - (void *)site_mod_start), + ((void *)iter - (void *)iter_mod_start)); entries++; + if (strcmp(modname, iter->site->modname)) { modct++; - ret = ddebug_add_module(iter_start, n, modname); + ret = ddebug_add_module(iter_mod_start, n, modname); if (ret) goto out_err; n = 0; modname = iter->site->modname; - iter_start = iter; + iter_mod_start = iter; + site_mod_start = site; } n++; } - ret = ddebug_add_module(iter_start, n, modname); + ret = ddebug_add_module(iter_mod_start, n, modname); if (ret) goto out_err; -- 2.29.2